A packet network that includes the distribution of timing information (time and frequency) between server and client devices can continue to operate in a holdover mode even when the server loses its primary timing reference based on GNSS. This is achieved by populating the packet network with some client devices that also have access to the same timing reference. These devices are used in a reverse timing transfer mode to provide a hack-up reference to the server and thereby provide a graceful solution to the problem of loss of reference.